In general, an integrated circuit refers to an electrical circuit contained on a single monolithic chip containing active and passive circuit elements. Integrated circuits are fabricated by diffusing and growing or depositing successive layers of various materials in a preselected pattern on a substrate. The materials can include semiconductive materials such as silicon, conductive materials such as metals, and dielectric materials such as silicon dioxide, silicon oxynitride, silicon carbide, silicon nitride and the like. Of particular significance, the various materials contained in integrated circuit chips are used to form almost all of the ordinary electronic circuit elements, such as resistors, capacitors, diodes, and transistors.
Integrated circuits are used in great quantities in electronic devices, such as digital computers, because of their small size, low power consumption, and high reliability. The complexity of integrated circuits range from simple logic gates and memory units to large arrays capable of complete video, audio and print data processing. Presently, however, there is a demand for integrated circuit chips to accomplish more tasks in a smaller space while having even lower operating voltage requirements.
As stated above, integrated circuit chips are manufactured by successively growing or depositing layers of different materials on a substrate. Typically, the substrate is made from a thin slice or wafer of silicon. The active and passive components of the integrated circuit are then built on top of the substrate. The components of the integrated circuit can include layers of different conductive materials such as metals and semiconductive materials surrounded by dielectric insulator materials. In attempting to improve integrated circuit chips, attention has been focused upon reducing the thickness of the layers while improving performance.
For instance, one area of circuit chip technology needing improvement is in the growth or deposition of insulator or dielectric materials used in the chips. Such an insulator material should have a very high resistivity, and sustainability of subsequent process steps and materials used in chip manufacturing. The dielectric insulator materials are incorporated into integrated circuits in order to reduce power dissipation when the circuit is in use.
Thin dielectric layers are being used routinely in the manufacturing of semiconductor devices for applications such as gates, capacitor dielectrics, besides various other uses. The most prevalent dielectric used in semiconductor devices is silicon dioxide, which can be grown through the reaction of oxygen and silicon at high temperature. Alternatively, water (H2O) can be reacted with silicon at high temperature to form silicon dioxide.
In the past, silicon dioxide layers have been grown in conventional batch furnaces and in rapid thermal processing systems. The use of rapid thermal processing systems offers the advantages of short time high temperature processing which provides process advantages over using conventional furnaces.
For instance, in the past, one particular method for forming and/or modifying a dielectric film on a semiconductor surface included the following steps:
a) exposing the semiconductor to a process gas comprising at least one reactive component at a predetermined first concentration C1 or partial pressure P1 to react with the semiconductor atoms. and/or molecules of the dielectric film while heating said semiconductor to form and/or modify said film or parts of it,
b) heating said semiconductor and/or said dielectric film to a first temperature T1 such that said reactive component and/or parts of it may diffuse through said dielectric film and/or into a surface region of said semiconductor to form said film on the surface of said semiconductor and/or to increase said film in thickness by reaction nearby a first interface between said semiconductor and said dielectric film, said reaction involves said reactive component and/or parts of it, semiconductor atoms and/or molecules from the dielectric film.
Such a method is known in the art and described e.g. by B. E. Deal and A. S. Grove in J. Appl. Phys. 36 (1965) 3770. Other references that discuss the formation of dielectric layers include U.S. Pat. No. 6,100,149; U.S. Pat. No. 6,323,143; U.S. Pat. No. 6,191,052; U.S. Pat. No. 5,904,523; U.S. Pat. No. 5,726,087 and U.S. Pat. No. 6,218,720 which are all incorporated herein by reference.
As described above, in order to produce advanced, fast acting devices, a need currently exists for producing dielectric layers having a minimal thickness. Controlled stoichiometry, a small concentration of structural defects and dangling bonds in bulk and at the interface of the dielectric layer and very small interface roughness of the adjacent interfaces are also required for optimization of dielectric layers in semiconductor devices. As the thickness of such dielectric layers decreases, however, significant difficulties arise in being able to properly and repeatedly create and/or modify thin layers, such as layers having a thickness of less than about 8 nm.
In fact, even conventional 30 second to 120 second heating cycles conducted in rapid thermal processing chambers that are used to produce dielectric layers according to the Deal and Grove model referenced above become too long to provide control sufficient to meet some of the requirements that are currently being specified.
Thus, a need currently exists for a repeatable process for producing and/or modifying thin dielectric layers that have improved electrical properties.